The purpose of this study is to find out whether METFORMIN decreases protein markers in colorectal tissue. This is a phase IIA study of the pharmacodynamics, safety and tolerability of Metformin in decreasing colorectal mucosa in patients with a history of colorectal adenomas in the past 3 years and a BMI >= 30, with decimals rounded to the nearest whole integer. Metformin as a potential chemopreventive agent for inhibition of the relevant molecular pathways involved in human colorectal carcinogenesis.